Magnetic disk device and automatic adaptation method of its parameter

ABSTRACT

In conventional technologies, when an automatic adaptation function of coefficient for equalization in a read/write channel IC is used, equalization coefficients obtained assuming a certain environment are used as initial values at the beginning of data reading. Therefore, if an environment in which the device operates actually differs seriously from the assumed environment, there is possibility that read errors are caused by inadequate coefficients for equalization at the beginning of data reading.  
     The object of the present invention is to provide a magnetic disk-device in which a deterioration of performance caused by the environmental variation, is suppressed by means of utilizing effectively an automatic adaptation function in a read/write channel IC.  
     A gate to produce a timing for the automatic adaptation of equalization coefficient is provided, a signal from the gate is given to a read-gate input terminal of read/write channel IC, and the gate for the automatic adaptation is opened before reading data from a destination sector to be read, and the automatic adaptation is started, hereby, coefficients for equalization are adapted to signal wave forms before reading data.

FIELD OF THE INVENTION

[0001] The present invention is related to a magnetic disk device,especially, a recording technology which provides an automaticadaptation function of parameter against a variation of the environmentaround the magnetic disk device and which gives high reliable magneticrecording.

BACKGROUND OF THE INVENTION

[0002] Today, with advancement of information-oriented society, anamount of information being processed by computers has increasedcertainly. Correspondingly it is strongly required to increase a storagecapacity of a magnetic disk device, and a successive improvement ofrecording density is indispensable.

[0003] To increase a recording density of a magnetic disk device, it isimportant to improve a performance of a read/write channel along with animproving performance of components such as a magnetic head and amagnetic disk medium. Especially, in recent years, PRML method has beenemployed in reproducing channel and performance of discriminating datafrom a low S/N reproduced signal has been improved. In this PRML method,interference between front part and rear part of reproduced signal isused effectively, therefore it is necessary to equalize a reproducedsignal wave to an ideal wave form and obtain proper interference of thewave form. When an equalization error is considerable, a discriminationerror occurs easily and reproduction of recorded data may not beexecuted normally. Therefore, the wave equalization technology isespecially important. Further, this wave equalization technology isimportant also in an improved PRML method.

[0004] Accordingly, when a variation of reproduced signal wave form iscaused by a variation in characteristics of a magnetic head or magneticdisk medium, etc., the adaptive equalization technology is combined inorder to equalize the reproduced signal wave form to the ideal waveform.

[0005] In usual adaptive equalization as shown in FIG. 1, anequalization error at each sampling point on the reproduced signal waveform is evaluated, and a value of equalization coefficient at each tapof transversal equalizer is learned and applied so as to minimize theequalization error. Further, in order to absorb a deviation ofsynchronization timing in a read operation caused by a variation ofread/write channel IC, various kinds of methods for automatic adaptationfunctions of parameters have also been applied. These technologiesrecently have advanced and applied rapidly to a wide range of digitaltechnology fields.

[0006] A technology in that parameters are automatically adjusted with aconstant time interval specified in advance instead of at each readoperation, is disclosed in Japanese patent unexamined publication Hei8-293165 (patent application Hei 7-96820).

[0007] This automatic adaptation of coefficient for equalization isstarted at the same time that reproducing data is started as shown inFIG. 2. Namely, automatic adaptation of equalization coefficient isexecuted using a signal wave received in a read-gate timing. Therefore,when the device has just started, or when some long time has passedafter previous adaptation, coefficients for equalization are not fullyadapted or adapted insufficiently.

[0008] When the equalization coefficients before being adapted haveinadequate values, there is a possibility of making some troubles suchthat a long time is required for adaptation or the read operation isabortive at the beginning of reading data. Therefore, it is requiredthat the equalization coefficients are to be set to the adequate initialconstants at the beginning of automatic adaptation. The initialconstants are learned at a shipment of the device and are recorded onthe management information area in which the initial values of variousparameters on the disk device are stored.

[0009] Coefficients for equalization are varied corresponding to avariation of characteristics of magnetic heads and magnetic disk media,the initial constants are to be set for each head. Furthermore,recently, the magnetic disk has a constitution in which the disk mediumis divided into plural zones radially and recording densities areoptimized for each zone. Therefore, the initial constants are requiredto be set for each zone.

[0010] Above-mentioned initial constants are applied as equalizationcoefficients to a signal processing circuit that processes firstread-out data just after the device has been started, after a head hasbeen switched to another, or after a zone has been changed.

[0011] In conventional technologies as described above, in order to keepparameters such as coefficients for equalization as adequate aspossible, the parameters learned at the shipment of the device isapplied to. However, when an environment in real use is differedseriously from one environment at the initial learning to another, thereproduced wave form is more varied from original one, the equalizationerror becomes large, and the read error occurs easily at the data-readoperation. This phenomenon makes the magnetic disk device seem to bedeteriorated in performance. However, even in this environment, ifcoefficient for equalization is learned again, it is often possible toread the data normally. As described above, the purpose of the presentinvention is to provide a magnetic disk device in which a deteriorationof performance caused by environmental variation is suppressed to theutmost.

SUMMARY OF THE INVENTION

[0012] To solve the problem described above, in a magnetic disk devicewhich contains a read/write channel IC having usual automatic adaptationfunction of parameter, a means to produce a gate signal for an automaticadaptation timing (gate signal 2 for the automatic adaptation in FIG. 3)and a logical-OR means (logical OR gate) having inputs said gate signal2 and read gate signal 1, are added in the logical circuit, and anoutput from said OR gate (logical OR gate signal 3) is given to a readgate input terminal of said read/write channel IC.

[0013] An example of each gate timing in adaptation of coefficient forequalization at data reading is shown in FIG. 3. In the configurationdescribed above, the gate which produces the timing for the automaticadaptation of coefficient for equalization is provided, the gate for theautomatic adaptation is opened toward the read command issued for datareading after seek has been completed and before data in destinationsector will be read, and the automatic adaptation is started. Hereby,the coefficients for equalization are adapted for a reproduced signalwave form as proper as possible till a beginning of data reading. As aresult, adequate coefficients for equalization can be obtained duringdata-reading operation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a figure for explaining that a signal wave form from adestination sector is adapted and come to be similar to an ideal waveform by the adaptation of coefficients for equalization.

[0015]FIG. 2 is a time chart showing a gate timing in the conventionalautomatic adaptation of coefficient for equalization.

[0016]FIG. 3 is a time chart showing a gate timing in automaticadaptation of coefficient for equalization when the present invention isapplied.

[0017]FIG. 4 is a plane view diagram of a magnetic disk device to whichthe present invention is applied.

[0018]FIG. 5 is a side view diagram of the magnetic disk device shown inFIG. 4.

[0019]FIG. 6 is a block diagram showing an example of a electroniccircuit embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A magnetic disk device to which the present invention is appliedis explained referring to FIG. 4 and FIG. 5.

[0021] A magnetic disk device comprises a sealed enclosure 4, disks 5which are rotating magnetic media, a spindle motor 6 which supports androtates the disk 5, a head assembly 7 having suspension arms andmagnetic heads which read out data from the disk 5, a swing arm(suspension arm 15) containing a pivot shaft 8 which supports the headassembly 7 and moves it on the disk, a voice coil motor 9 which drivesthe swing arm, an electronic circuit 10 which lets the magnetic headwrite data to the disk 5 and read data from the disk 5, and a printedcircuit board 11 which connects electrically to a controller to controloperation of the spindle motor 6 and the voice coil motor 9. The disk 5,the spindle motor 6, the head assembly 7, the voice coil motor 9, andthe printed circuit board 11 exists inside the enclosure 4 and aresealed within the enclosure 4.

[0022] The spindle motor 6 comprising a hub which fixes the disk 5 atits outer-circumference, a rotor and a stator which are built in the hub(an in-hub type motor), is built on a base plate of the enclosure 4.However, in the embodiment of the present invention, the spindle motoris not limited to the in-hub type motor.

[0023] The disk 5 is a important component which determines data storagecapacity of the magnetic disk device. For example, the device comprisesone or several disks corresponding to storage capacity. In this magneticdisk device, the disk 5 and a disk spacer 12 (FIG. 5) are insertedalternately on the hub. A disk clamp 13 fixes the disk 5 on the spindlemotor 6 by clamping a pile of disks in the axial direction-of thespindle-motor 6.

[0024] There are several swing arms corresponding to the number ofdisks, which comprises plural sliders 14 carrying magnetic heads, andplural suspension arms 15 (FIG. 4). The swing arms are fixed to the baseplate through the pivot shaft 8 so as to rotate freely.

[0025] Next, a constitution of a read channel in the magnetic diskdevice which is an embodiment of the present invention, is explainedreferring to a block diagram shown in FIG. 6.

[0026] This read channel at least comprises the following: a magnetichead which writes data to a recording medium and reads data from therecording medium, a read/write amplifier which puts out a read signal ata read-output terminal and puts out a write signal to the magnetic head,a read/write channel IC 16 which has an automatic adaptation function ofcoefficients for equalization, a first controller 17 which produces aread gate signal 1 (FIG. 3), a second controller 18 which issynchronized with said first controller and produces a gate signal 2 forautomatic adaptation (FIG. 3), and a logical OR means 19 which producesan OR gate signal 3 being logical OR of the read gate signal 1 and thegate signal 2 for automatic adaptation.

[0027] Next, the operation of the read channel constructed above isexplained.

[0028] The first controller 17 generates a timing signal for writing andreading data by the magnetic head, and a clock signal which is a basetiming signal for the operation of the read/write channel IC 16 and thesecond controller 18. Furthermore, the first controller 17 also controlsthe read gate signal 1 in FIG. 3 which is timing to take in the readsignal. The second controller 18 synchronizes to the first controller 17utilizing the clock signal and controls the gate signal 2 for automaticadaptation in FIG. 3. A logical OR gate signal 3 is produced byexecuting logical OR with above two gate signals using the logical ORmeans 19, and the gate signal 3 is given to the read/write channel IC16. The read gate signal 1 which is controlled by the first controller17 is also given to the read/write channel IC 16.

[0029] The read signal which is reproduced by the magnetic head, isamplified by the read/write amplifier to such level as the read/writechannel IC can recognize. The amplified signal is given to theread/write channel IC 16 and utilized for the automatic adaptation ofequalization coefficient with above-mentioned logical OR gate timing.Simultaneously, this signal is translated to data in the read/writechannel IC 16 in timing of the read gate signal 1 and the data is putout from the read/write channel IC 16 to next read process. In thistranslation to data, the newly equalized coefficients is applied usingthe logical OR gate signal 3 which has been opened earlier than the readgate 1. The equalization coefficients are established in the first openof the logical OR gate 3.

[0030] The read gate signal 1 and the gate signal 2 for automaticadaptation may be produced by same controller. The logical OR functionby the logical OR means 19 may be installed in a program of the firstcontroller 17 or the second controller 18. In this case, the independentlogical OR means 19 as a hardware is unnecessary. In addition, when aninput terminal for automatic adaptation gate to control automaticadaptation is provided in the read/write channel IC besides an usualread gate input terminal, the logical OR means 19 is unnecessary and theread gate signal 1 may be put in the read gate input terminal and thegate signal 2 for automatic adaptation may be put in the input terminalfor automatic adaptation gate.

[0031] Next, in the magnetic disk device as an embodiment of the presentinvention, conditions in which the automatic adaptation function becomeseffective are explained.

[0032] The coefficients for equalization are required to be set toinitial constants corresponding to the zone on the magnetic disk mediumby one head switched to another, or by a seek operation for another zoneby the actuator.

[0033] On the other hand, the equalization coefficients are almost samein the same zone, the same head, and the same environment. Therefore,when same head seeks a track in same zone, it is possible to use thesame equalization coefficients which have been adapted by that time.Accordingly, in this case, it is unnecessary to execute the automaticadaptation by making the automatic adaptation gate open before readingdata from a destination sector.

[0034] When a magnetic head is switched to another head or when a trackin another zone is sought by the actuator, if a latency time (a waitingtime in rotation) until a start of reading data from the destinationsector is too short to execute the automatic adaptation efficiently, itis unnecessary to execute the automatic adaptation of the coefficientfor signal wave equalization by making the automatic adaptation gateopen earlier before reading data from a destination sector.

[0035] Except above two cases in which the automatic adaptation functionis not applied, the automatic adaptation function is activated bydefault.

[0036] In the automatic adaptation function of the coefficient forequalization, signals received while the automatic adaptation gate isopened, are treated as only wave forms not as data which mean contentsof the signals. Therefore, signal wave forms used in the automaticadaptation ate considered to be sufficient if the signal wave forms arerecorded in any area where the wave forms can be read from, and it isnot restricted to the wave forms recorded in user data area. Namely,either next save forms will do: the signal wave forms which are recordedpreviously on the magnetic disk medium at shipment of the device, andthe signal wave forms which are reproduced from data recorded by usersafter the shipment of the device. The latter signal wave forms arebetter for use in order to obtain high accuracy in signal waveequalization.

[0037] Timing to open the gate for the automatic adaptation of theequalization coefficients are as follows

[0038] 1) at timing when a seek complete signal (it means that seekoperation has finished normally) is detected; and

[0039] 2) at timing when the magnetic head comes over a sector whichlocates a several sectors ahead from the destination sector to be read.

[0040] In both timings described above, the equalization coefficientsare adapted actually while the logical OR gate which is logical OR ofthe read gate signal 1 and the gate signal 2 for the automaticadaptation is opened; therefore, the timing when the gate 2 is closed isnot limited to the timing when the read gate signal 1 is detected, butit is allowed to be an arbitrary timing after the operation timerequired for completion of the automatic adaptation has been ensured.

[0041] Start timing of the automatic adaptation operation in theread/write IC which has the automatic adaptation function has beenprovided before required data are read from a destination sector;hereby, various parameters have been able to be adapted by the automaticadaptation before the data are read from the destination sector. Amagnetic disk device having high reliability against the variation ofenvironment can be provided.

[0042] Having described a preferred embodiment of the invention withreference to the accompanying drawings, it is to be understood that theinvention is not limited to the embodiments and that various changes andmodifications could be effected therein by one skilled in the artwithout departing from the spirit or scope of the invention as definedin the appended claims.

What is claimed is:
 1. An automatic adaptation method in a magnetic diskdevice, comprising the steps of: 1st step for a signal to open a gate isissued; 2nd step for a signal to set parameter is issued correspondingto the gate signal issued in the 1st step; and 3rd step for a signal toopen a gate to read data is issued after 2nd step.
 2. An automaticadaptation method in a magnetic disk device, comprising the steps of:1st step for a signal showing that a seek is completed is put out; 2ndstep for a signal to open a gate is issued; 3rd step for a signal to setparameter is issued corresponding to the gate signal issued in the 2ndstep; and 4th step for a signal to open a gate to read data is issuedafter 3rd step.
 3. The automatic adaptation method according to claim 1or claim 2 , wherein said parameter is a coefficient for equalizationand said signal to open a gate to read data is a read gate signal. 4.The automatic adaptation method according to claim 1 or claim 2 ,wherein said signal to set parameter is a signal provided beforehand ora signal recorded afterward.
 5. The automatic adaptation methodaccording to claim 4 , wherein said signal provided beforehandoriginates from a signal obtained from a magnetic recording medium in amagnetic disk device.
 6. The automatic adaptation method according toclaim 4 , wherein said signal recorded afterward originated fromparameter which has been learned by the magnetic disk device.
 7. Amagnetic disk device having a function for an automatic parameteradaptation, comprising: a magnetic recording medium being rotatablysupported; a spindle motor rotating said magnetic recording medium; amagnetic head recording and reproducing data to and from said magneticrecording medium; an actuator moving said magnetic head onto anappointed position on said magnetic recording medium; and a controlleradapting parameters automatically using a signal from said magnetichead, and communicating a signal from said magnetic head into anothercircuit; wherein corresponding to a read data request, said controllerhas adapt said parameters automatically before said data is read.
 8. Amagnetic disk device having a function for an automatic parameteradaptation, comprising: a magnetic recording medium being rotatablysupported; a spindle motor rotating said magnetic recording medium; amagnetic head recording and reproducing data to and from said magneticrecording medium; an actuator moving said magnetic head onto anappointed position on said magnetic recording medium; and a controlleradapting parameters automatically using a signal from said magnetichead, and communicating a signal from said magnetic head into anothercircuit; wherein said controller has adapt said parameters automaticallycorresponding to a read data request, after said magnetic head has beenpositioned completely to an appointed position on said magneticrecording medium, and before said data is read.
 9. The magnetic diskdevice according to claim 7 or claim 8 , wherein said parameters arecoefficients for signal equalization.
 10. The magnetic disk deviceaccording to claim 7 or claim 8 , wherein said controller comprises: aread/write amplifier amplifying an output signal from said magnetic headand giving a signal to said magnetic head; a read/write channel IC beingconnected electrically to said read/write amplifier and having theautomatic adaptation function of the coefficient for signalequalization; and a logical circuit giving a signal to said read/writechannel IC for said automatic adaptation function.
 11. The magnetic diskdevice according to claim 7 , wherein “before said data is read” means“before a read-gate signal is detected”.
 12. The magnetic disk deviceaccording to claim 8 , wherein “after said magnetic head has beenpositioned completely” means “after a seek-complete signal has beendetected”.